Currently, polyolefin resins are used widely in various fields, such as automobiles, household electric appliances, stationery, films, food containers, etc. However, functions suited for the respective usages cannot be obtained with polyolefin resins alone and therefore various additives are blended.
Conventionally, as methods of improving surface characteristics, such as water repellency, lubricating property, mold release property, etc., of polyolefin resins, methods of kneading a substance having a surface characteristic improving effect, such as a silicone compound, etc., into a polyolefin resin, methods of coating such a substance on a surface of a polyolefin resin, etc., have been carried out. Among such methods, kneading methods are used industrially due to being simple and not increasing manufacturing processes and being high in the effect of improving the surface characteristics of polyolefin resins. However, in cases of simply kneading a silicone compound or other substance having a surface characteristic improving effect as it is into a polyolefin resin, it may be difficult to perform uniform kneading at times and further, bleed-out may occur and preclude the maintenance of sustained water repellency. Surface modifiers, which are polypropylene resin compositions with water repellency that are obtained by bonding a polypropylene resin, having compatibility with polyolefin resins, and a silicone compound or other substance having a surface characteristic improving effect, have thus been developed.
As conventional arts related to a polypropylene resin composition (surface modifier) with water repellency that is obtained by bonding a polypropylene resin and a silicone compound, a method for manufacturing a polypropylene resin molded article by melting and kneading a composition made up of polypropylene, an organopolysiloxane having a vinyl group, and an organic peroxide and thereafter performing molding (see Patent Document 1), a method for manufacturing a polypropylene resin composition by heating and kneading a polypropylene resin and a polyorganosiloxane, containing at least one silicon-atom-bonded alkenyl group in each molecule, without the presence of a radical forming catalyst, to chemically bond the polyorganosiloxane to the polypropylene resin and then performing heating and kneading upon adding an antioxidant (see Patent Document 2), etc., have been disclosed.
However, with the method of Patent Document 1, chemical bonding between the polypropylene and the organopolysiloxane having a vinyl group does not progress uniformly because these two components are not readily miscible with each other, and there is a problem in that portions of the organopolysiloxane bond chemically to each other to form aggregates that deteriorate the appearance. A surface modifier that is a more preferable polypropylene resin was thus desired.
Patent documents are as se bellow.
[Patent Document 1] Japan Patent No. 2516283
[Patent Document 2] Japan Patent No. 3597578